Depends what they're fighting I suppose.
Ripley, in Aliens, was already hardcore, but somehow recieved a badass-level upgrade by putting the power suit ON. I think the willingness to a/ wear and use something that allows you to demolish a building with one hand, b/ requires you be locked into it as a massive, lumbering, non stealthy sitting duck, c/ signifies that you're probably going to be fighting enemies so tough that unsuited soldiers wouldn't have the slightest chance against... and neither will you if your suit is knocked out and you're trapped in it - means that you deserve at least a little kudos.
That's why, e.g. Quarich from Avatar is definitely on the badass list, despite otherwise being a total fucknut. The man is a total hardcase, and with a tiny attitude adjustment in a different setting would be a Duke Nukem style antihero. He's trying to do a bit of vegetation clearance in the face of heavy opposition from 8ft tall, almost unkillable aliens who live in a poisonous atmosphere, and to get the job done will willingly brave asphyxiation by going out into the world sans mask, get his face slashed up, and eventually - when his demonstrably iron-pumped muscles probably aren't going to cut it - suit up in what is basically a walking pickup truck (with more strength but less manouevrability - or resilience!) and ride it to earth A-team style out of the burning wreckage of a crippled dropship to continue kicking what he sees as some righteous ass, even though he'll probably die in the process. The suit just means he can kick butt a little longer and harder before expiring, which might be all the difference that's required to finish the job.
Now, that's pretty god damned badass to me.
Similarly the Warhammer space marines. They're fighting unspeakable horrors that could rip your lungs out through your heart just by thinking about looking at you. The vertical-tank type armour is pretty much a requisite ... as is the guts to go out fighting that kind of foe in the first place, rather than turning tail and getting on the first transport ship to the other end of the galaxy. I mean, the powersuit may be armoured, but that's a bit token and only good against lesser enemies wielding conventional ranged or bladed weapons. It's mostly there so you can continue mashing slaaneshi devotees into the permafrost a little longer and more forcefully before one of the more powerful ones casts some kind of spell or does a memetic dance that causes your brain to melt out of your nose.
The most hardcore marine is recognisable by ditching the helmet, because it restricts vision, has no bearing on strength, and really doesn't enhance your survivability that much.